﻿/*
 * Copyright 2001,2004-2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This package is based on the work done by Keiron Liddle), Aftex Software
 * <keiron@aftexsw.com> to whom the Ant project is very grateful for his
 * great code.
 */

namespace SharpCompress.Compressors.BZip2;

/**
  * A simple class the hold and calculate the CRC for sanity checking
  * of the data.
  *
  * @author <a href="mailto:keiron@aftexsw.com">Keiron Liddle</a>
  */

internal class CRC
{
    public static int[] crc32Table =
    {
        0x00000000,
        0x04c11db7,
        0x09823b6e,
        0x0d4326d9,
        0x130476dc,
        0x17c56b6b,
        0x1a864db2,
        0x1e475005,
        0x2608edb8,
        0x22c9f00f,
        0x2f8ad6d6,
        0x2b4bcb61,
        0x350c9b64,
        0x31cd86d3,
        0x3c8ea00a,
        0x384fbdbd,
        0x4c11db70,
        0x48d0c6c7,
        0x4593e01e,
        0x4152fda9,
        0x5f15adac,
        0x5bd4b01b,
        0x569796c2,
        0x52568b75,
        0x6a1936c8,
        0x6ed82b7f,
        0x639b0da6,
        0x675a1011,
        0x791d4014,
        0x7ddc5da3,
        0x709f7b7a,
        0x745e66cd,
        unchecked((int)0x9823b6e0),
        unchecked((int)0x9ce2ab57),
        unchecked((int)0x91a18d8e),
        unchecked((int)0x95609039),
        unchecked((int)0x8b27c03c),
        unchecked((int)0x8fe6dd8b),
        unchecked((int)0x82a5fb52),
        unchecked((int)0x8664e6e5),
        unchecked((int)0xbe2b5b58),
        unchecked((int)0xbaea46ef),
        unchecked((int)0xb7a96036),
        unchecked((int)0xb3687d81),
        unchecked((int)0xad2f2d84),
        unchecked((int)0xa9ee3033),
        unchecked((int)0xa4ad16ea),
        unchecked((int)0xa06c0b5d),
        unchecked((int)0xd4326d90),
        unchecked((int)0xd0f37027),
        unchecked((int)0xddb056fe),
        unchecked((int)0xd9714b49),
        unchecked((int)0xc7361b4c),
        unchecked((int)0xc3f706fb),
        unchecked((int)0xceb42022),
        unchecked((int)0xca753d95),
        unchecked((int)0xf23a8028),
        unchecked((int)0xf6fb9d9f),
        unchecked((int)0xfbb8bb46),
        unchecked((int)0xff79a6f1),
        unchecked((int)0xe13ef6f4),
        unchecked((int)0xe5ffeb43),
        unchecked((int)0xe8bccd9a),
        unchecked((int)0xec7dd02d),
        0x34867077,
        0x30476dc0,
        0x3d044b19,
        0x39c556ae,
        0x278206ab,
        0x23431b1c,
        0x2e003dc5,
        0x2ac12072,
        0x128e9dcf,
        0x164f8078,
        0x1b0ca6a1,
        0x1fcdbb16,
        0x018aeb13,
        0x054bf6a4,
        0x0808d07d,
        0x0cc9cdca,
        0x7897ab07,
        0x7c56b6b0,
        0x71159069,
        0x75d48dde,
        0x6b93dddb,
        0x6f52c06c,
        0x6211e6b5,
        0x66d0fb02,
        0x5e9f46bf,
        0x5a5e5b08,
        0x571d7dd1,
        0x53dc6066,
        0x4d9b3063,
        0x495a2dd4,
        0x44190b0d,
        0x40d816ba,
        unchecked((int)0xaca5c697),
        unchecked((int)0xa864db20),
        unchecked((int)0xa527fdf9),
        unchecked((int)0xa1e6e04e),
        unchecked((int)0xbfa1b04b),
        unchecked((int)0xbb60adfc),
        unchecked((int)0xb6238b25),
        unchecked((int)0xb2e29692),
        unchecked((int)0x8aad2b2f),
        unchecked((int)0x8e6c3698),
        unchecked((int)0x832f1041),
        unchecked((int)0x87ee0df6),
        unchecked((int)0x99a95df3),
        unchecked((int)0x9d684044),
        unchecked((int)0x902b669d),
        unchecked((int)0x94ea7b2a),
        unchecked((int)0xe0b41de7),
        unchecked((int)0xe4750050),
        unchecked((int)0xe9362689),
        unchecked((int)0xedf73b3e),
        unchecked((int)0xf3b06b3b),
        unchecked((int)0xf771768c),
        unchecked((int)0xfa325055),
        unchecked((int)0xfef34de2),
        unchecked((int)0xc6bcf05f),
        unchecked((int)0xc27dede8),
        unchecked((int)0xcf3ecb31),
        unchecked((int)0xcbffd686),
        unchecked((int)0xd5b88683),
        unchecked((int)0xd1799b34),
        unchecked((int)0xdc3abded),
        unchecked((int)0xd8fba05a),
        0x690ce0ee,
        0x6dcdfd59,
        0x608edb80,
        0x644fc637,
        0x7a089632,
        0x7ec98b85,
        0x738aad5c,
        0x774bb0eb,
        0x4f040d56,
        0x4bc510e1,
        0x46863638,
        0x42472b8f,
        0x5c007b8a,
        0x58c1663d,
        0x558240e4,
        0x51435d53,
        0x251d3b9e,
        0x21dc2629,
        0x2c9f00f0,
        0x285e1d47,
        0x36194d42,
        0x32d850f5,
        0x3f9b762c,
        0x3b5a6b9b,
        0x0315d626,
        0x07d4cb91,
        0x0a97ed48,
        0x0e56f0ff,
        0x1011a0fa,
        0x14d0bd4d,
        0x19939b94,
        0x1d528623,
        unchecked((int)0xf12f560e),
        unchecked((int)0xf5ee4bb9),
        unchecked((int)0xf8ad6d60),
        unchecked((int)0xfc6c70d7),
        unchecked((int)0xe22b20d2),
        unchecked((int)0xe6ea3d65),
        unchecked((int)0xeba91bbc),
        unchecked((int)0xef68060b),
        unchecked((int)0xd727bbb6),
        unchecked((int)0xd3e6a601),
        unchecked((int)0xdea580d8),
        unchecked((int)0xda649d6f),
        unchecked((int)0xc423cd6a),
        unchecked((int)0xc0e2d0dd),
        unchecked((int)0xcda1f604),
        unchecked((int)0xc960ebb3),
        unchecked((int)0xbd3e8d7e),
        unchecked((int)0xb9ff90c9),
        unchecked((int)0xb4bcb610),
        unchecked((int)0xb07daba7),
        unchecked((int)0xae3afba2),
        unchecked((int)0xaafbe615),
        unchecked((int)0xa7b8c0cc),
        unchecked((int)0xa379dd7b),
        unchecked((int)0x9b3660c6),
        unchecked((int)0x9ff77d71),
        unchecked((int)0x92b45ba8),
        unchecked((int)0x9675461f),
        unchecked((int)0x8832161a),
        unchecked((int)0x8cf30bad),
        unchecked((int)0x81b02d74),
        unchecked((int)0x857130c3),
        0x5d8a9099,
        0x594b8d2e,
        0x5408abf7,
        0x50c9b640,
        0x4e8ee645,
        0x4a4ffbf2,
        0x470cdd2b,
        0x43cdc09c,
        0x7b827d21,
        0x7f436096,
        0x7200464f,
        0x76c15bf8,
        0x68860bfd,
        0x6c47164a,
        0x61043093,
        0x65c52d24,
        0x119b4be9,
        0x155a565e,
        0x18197087,
        0x1cd86d30,
        0x029f3d35,
        0x065e2082,
        0x0b1d065b,
        0x0fdc1bec,
        0x3793a651,
        0x3352bbe6,
        0x3e119d3f,
        0x3ad08088,
        0x2497d08d,
        0x2056cd3a,
        0x2d15ebe3,
        0x29d4f654,
        unchecked((int)0xc5a92679),
        unchecked((int)0xc1683bce),
        unchecked((int)0xcc2b1d17),
        unchecked((int)0xc8ea00a0),
        unchecked((int)0xd6ad50a5),
        unchecked((int)0xd26c4d12),
        unchecked((int)0xdf2f6bcb),
        unchecked((int)0xdbee767c),
        unchecked((int)0xe3a1cbc1),
        unchecked((int)0xe760d676),
        unchecked((int)0xea23f0af),
        unchecked((int)0xeee2ed18),
        unchecked((int)0xf0a5bd1d),
        unchecked((int)0xf464a0aa),
        unchecked((int)0xf9278673),
        unchecked((int)0xfde69bc4),
        unchecked((int)0x89b8fd09),
        unchecked((int)0x8d79e0be),
        unchecked((int)0x803ac667),
        unchecked((int)0x84fbdbd0),
        unchecked((int)0x9abc8bd5),
        unchecked((int)0x9e7d9662),
        unchecked((int)0x933eb0bb),
        unchecked((int)0x97ffad0c),
        unchecked((int)0xafb010b1),
        unchecked((int)0xab710d06),
        unchecked((int)0xa6322bdf),
        unchecked((int)0xa2f33668),
        unchecked((int)0xbcb4666d),
        unchecked((int)0xb8757bda),
        unchecked((int)0xb5365d03),
        unchecked((int)0xb1f740b4),
    };

    public CRC() => InitialiseCRC();

    internal void InitialiseCRC() => globalCrc = unchecked((int)0xffffffff);

    internal int GetFinalCRC() => ~globalCrc;

    internal int GetGlobalCRC() => globalCrc;

    internal void SetGlobalCRC(int newCrc) => globalCrc = newCrc;

    internal void UpdateCRC(int inCh)
    {
        var temp = (globalCrc >> 24) ^ inCh;
        if (temp < 0)
        {
            temp = 256 + temp;
        }
        globalCrc = (globalCrc << 8) ^ crc32Table[temp];
    }

    internal int globalCrc;
}
